1. Field of the Invention
The present invention relates to an image forming apparatus on which a container containing toner is mounted.
2. Description of the Related Art
An electrophotographic image forming apparatus forms a toner image by developing an electrostatic latent image formed on a photosensitive member with a developer (hereinafter, referred to as toner) in a developing unit. The developing unit can store only a limited amount of toner inside. The developing unit thus needs to be replenished, when needed, with toner from a container detachably mounted on the main body of the image forming apparatus.
US Patent 2014/0016967 discusses a container that includes a rotation unit to be driven to rotate, a pump unit configured to change an internal pressure of a containing unit containing toner to discharge the toner from the containing unit, and a conversion unit configured to convert rotational motion of the rotation unit into expansion and contraction of the pump unit. The container discharges the toner in the containing unit by making the pump unit expand and contract according to the rotation of the container. More specifically, when the pump unit expands, air sucked in from a discharge port loosens the toner in the containing unit. The pump unit is then compressed to pressurize the containing unit, whereby the air in the container pushes the toner covering the discharge port out of the discharge port.
To accurately control the amount of toner discharged from such a container, the rotation speed of the container needs to be accurately controlled. The rotation speed may be controlled, for example, by measuring the time during which a predetermined portion formed on the container in the direction of rotation is detected while the container is rotated, and controlling the rotation speed of the container based on the measured time. However, with such a configuration, the rotation speed of the container can vary even while the predetermined portion of the container is being detected, depending on the rotation angle of the container when the container is mounted on a mounting unit. As a result, it is not possible to accurately measure the time during which the predetermined portion of the container is detected, or precisely control the rotation speed of the container.